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Beginner

small mtu

we ware in nexus environment, if we set up mtu size less than 9000, would it cause packet loss? if mtu size less than 9000, does cisco switch put it in the queue for excessive queue if mtu size less than 9000,

does fragmentation cause jitter?

3 REPLIES 3
Cisco Employee

Re: small mtu

Good day,

 

 

If you configure MTU to 9000 bytes, that just means for the Nexus that if it receives a one packet with a size above 9000 bytes, the Nexus will fragment it using its CPU and "break" the packet in two parts, then send them out. 

Based off the fact that fragmentation happens with the CPU, forwarding will be a bit slower only for those specific packets with a size above the MTU, which will in turn reflect as slowness from an end host standpoint.

You may want to take a packet capture of some links in your environment to check the current size of the usual packets in your network, and then make a decision.

 

Hope this helps.

 

Eduardo.

 

 

 

 

VIP Advocate

Re: small mtu

Hi, 

By default, all L3 devices (Router and Firewall) are configured with MTU 1500 and It is only accepted by ISP. If will increase or decrease the MTP on gateway label then will face many issues related to Internet or speed. But you had changed on Nexus switch so It is chance the increase your Gateway Lebal device process for fragmentation packets etc. 

(I hope) You are talking about Jumbo Frame. It is used for local storage devices as NAS or other. So It is chance to increase some delay (fragmentation time) and increase packet queue if your packet is more then 900.

 

Thanks,

Deepak Kumar

Deepak Kumar 

Regards,
Deepak Kumar,
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Beginner

Re: small mtu

can you recomend the article to use wireshark to analyze the problem that slow due to small mtu issue
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